Nathaniel dunn



(ModeL) N.DUNN.. TENSION DEVICE FOR SEWINGMAGHINES.

No. 243,874. Patented July 5,1881.

WITNESSES: Q INVENTEIR:

w I WW '1, PETERS. PboloLithogrApMr. wmm nm o c.

UNITED STATES PATENT OFFICE.

NATHANIEL DUNN, OF NEW YORK, N. Y.

TENSION DEVICE FOR SEWING-MACHINES.

SPECIFICATION forming part of Letters Patent No. 243,874, dated July 5, 1881;

i Application filed May 24,1880. (Modeh) To all whom it may concern Be it known that I, NATHANIEL DUNN, of New York city, New York, have invented certain new and useful Improvements in Tension Devices for Sewing-Machines, of which the following is a specification.

My invention aims to provide an automatic tension, more particularly for lock-stitch machines, but also adaptable to sin gle'thread machines, which may be readily attached to existing machines and be operated by the action of the needle-bar in such manner as to positively clamp and release the thread at proper points in the stroke of the needle, so as to insure a stitch of proper tightness on any kind of work, either thick or thin, without any special adjustment for the same.

To this end my invention embodies a number of novel features, as hereinafter fully set forth.

Figure 1 of the drawings annexed is a plan view of myimproved tension attachment, and Fig. 2 is a side elevation thereof attached to the machine. a

As illustrated in the drawings, the attachment is mounted on the end of the sewingmachine arm toward the needle-bar, inclining upwardly at its front end and resting upon the head of the arm, to which it is fastened at the points a a by screws or other suitable means, and is also fastened to the arm bya support, (o

The base-plate a of the device is fitted with longitudinal ways I) b, in which a slide, f, is guided, and is also formed with an upright, 0, to which an elbow-lever, d, is pivoted. The long arm of this lever projects toward the needle-bar, while the short arm extends toward the base-plate and is pivoted to a rod, 6, which is connected at its opposite end with the rear end of the slide f. At the opposite side of the base-plate is fixed a spring-jaw, g, which extends over a boss, h, at about its middle, while its free extremity projects over the slide f. A cam-flange, 2', projects from the slide f toward the free end of the spring. This cam-flange, when it moves forward with the slide, passes over the end of the spring and presses the same upon the boss, and then passing beyond the spring allows it to rise from contact with the boss by its own elasticity, while the cam, on its return-stroke, passes under the spring, lifting it from the boss preparatory for another stroke of the needle. A take-up, k, pivoted to the base at 70, is formed with a cam-slot, 1, into which a pin, f, projecting from the slide f extends, so that the take-up is vibrated by the motion of the slide. The frontend of the baseplate is provided with a broad hook, m, and a catch-notch, n, and the take-up is terminated with an eye, j, which vibrates over this hook and its adjoined notch.

On the needle-bar of the machine is fastened a cap or block, 0, which is perforated with an eye at one side, in which the projecting arm of the elbow-lever d is received, and by which the lever, together with the other mechanism of the tension, is actuated by the motion of the needle-bar, as will be understood by the drawings. The cap 0 is perforated with another hole, o, to admit the passage of the thread to the needle a little above the usual thread-hole in the bar. The thread, in passing from the spool to the needle, passes first over the boss h and under the spring g, and also under the guide-hookspp and the hook m, thence through the eye of the take-up and through the eye 0 of the cap 0 to the needle, and it will hence be observed that when the sliding cam t passes over and presses down the springg the thread will be held tight, and when the cam returns or passes under the spring the thread will be entirely released. The parts of this device are so arranged and proportioned that when the needle is at the end of its downstroke the cam i will be out of contact with the clamp-spring g, as shown in Fig. 2, and hence the latter will be released from the thread, while the eye of the take-up will be at the entrance of the notch a. As the needle-bar commences to rise, the cam moves toward the clamp-spring g, and the take-up moves quickly and catches the thread into the notch a, just before the cam passes over and clamps the spring upon the thread, which, hence, now becomes held both at the notch and atthe clamp. The take-up now continues to advance 'rapidly, and takes up the shuttle-slack of the needle-thread, and as the needle-bar now rises rapidly the take-up retires, removes the thread from the notch, and allows the needle-bar to continue the taking up of the slack. As the needle-bar approaches the top of its stroke, where all the slack be comes taken up, it then draws on the thread this mechanism, as may be observed, the proper tightness or tension will always be given to the stitch in a positive and automatic manner, whether the work be thick or thin, without requiring any adjustments for such difference of thickness, as required by the common frictional tensions.

It may be observed, further, that while the stitch is being tightened by the upstroke of the needle-bar the thread is not drawn too positively, which might tend to break it, for the reason that the outer end of the take-up is formed to act as a spring with sufficient elasticity to yield slightly and ease the strain upon the thread, so as to render the pull on the thread sufficiently forcible to properly tighten the stitch in all cases, yet not so rigid as might cause a break in some cases.

The spring g and boss 7b, 850., are mounted on a plate, 1, which is pivoted to the base at s, and fastened at any desired adjustment by the screw t passing through a slot in the plate, so that by this means, as will be-observed, the loose end of the spring may be adjusted in true relation to the cam j" to effect the clamping action at the proper moment. Two vertical screws, to 42, passing through the plate 1' and bearin g upon the base-plate respectively at the inner and outer ends of the plate, enable the spring to be adjusted vertically to or from the cam 73, so as to cause the thread to be griped with more or less force. The spring 9 is curved transversely at its inner part and is flat at its fixed end, so as to get the desired elasticity without having the spring yield all along its length. A leather or other cushion, w, on the cam-slide receives the recoil of the spring y when released by the cam, and prevents the rinlgin g sound which would be otherwise emitter In machines in which the spool is moved with the needle-baras in some single-thread machines-the movement of the parts of the tension device may be reversed-that is, the cam i may be stationary and the spring g, with the boss h, movable-with the same effect as in the movement required in the lock-stitch machines.

What I claim as my invention is-- 1. The combination, in a thread-tension device for sewing-machines, of the actuating-lever d, vibrating slide or carrier f, provided with the cam t, and clamp-jaw g, arranged and operating substantially as hereinset forth.

2. In a sewing-machine thread-tension device, the combination, with a clamp acting to hold and release the thread at certain points in the stroke of the needle, of a take-up distinct from .the needle-bar and having a distinct motion, arranged between the saidclam'p and the needle, together with a catch-notch over which the take-up vibrates, and means, such as described, for operating said clamp and take-up, whereby the thread becomes engaged with said notch when the take-up advances and is released therefrom when the takeup retires, substantially as herein shown and described.

3. In a sewing-machine thread-tension, the combination, with a thread'clam p arranged between the spool and the needle, and of mechanism operating the same to clamp and release the thread at certain points in the stroke of the needle, of a yielding spring arranged between the said clamp and the needle, and through or over which the thread is passed from the clamp to the needle, snbstantiallyas and for the purpose herein set forth.

4. The combination, in a sewing-machine thread-tensiomof the spring-jaw g, the reciprocatin g slide f, provided with the cam 41, and the take-up 7c, actuated by said slide, with devices for operating said cam-slide from the needlebar of the machine or other driving part thereof, substantially as herein set forth.

NATHANIEL DUNN.

. Witnesses:

EDWARD H. WALEs,

OHAs. M. Hreenvs. 

